Are the gigantocellular tegmental field neurons responsible for paradoxical sleep?

We have compared the effects of electrolytic and kainic acid lesions of the pontine gigantocellular tegmental field (FTG) upon paradoxical sleep (PS). Following bilateral electrolytic destruction of the ventrolateral part of the FTG, there was an almost total suppression of PS which lasted at least for 5 weeks. Muscular atonia was absent and ponto-geniculo-occipital (PGO) activity was reduced by 80% in the few remaining episodes of PS. Contrary to to these effects, total neuronal cell loss of the FTG induced by bilateral kainic acid injection was not followed by a significant quantitative and qualitative alteration of PS. These results indicate that the neurons located within the FTG are not critical for the generation of both phasic and tonic components of PS. Elimination of this state of sleep after electrolytic destruction of the ventrolateral pontine reticular formation can be explained by interruption of fibers connecting the region of the locus coeruleus complex and the bulbar reticular formation.